Process of applying hard surfacing material to metal bodies



Jan. 20, 1953 c, LLIO 2,626,221

PROCESS OF APPLYING HARD SURFACIN MATERIAL. TO METAL BODIES Filed Feb.26, 1948 CHARLL'J hf. ELL/0T7 MIVENTOR ATTORNE Y5 Patented Jan. 20, 1953PROCESS OF APPLYING HARD SURFACING MATERIAL TO METAL BODIES.

Charles H. Elliott, Houston, Tex., assignor to Reed Roller Bit Company,Houston, Tex., a corporation of Texas Application February 26, 1948,Serial No. 10,974

2 Claims.

plication of granular hard materials to the surface to be hardened.

Heretofore it has been the practice to coat the surface to be hardenedwith a pasty binder and then embed the granular hard material in thebinder. Acetylene hand torches are then employed to heat a smallincrement of the surface at a time to the point that the granularheating material becomes bonded to the surface. This process is known aspuddling in the granular material. From-the standpoint of service,materials processed in this fashion have been satisfactory, but theprocess is both slow and expensive.

It has been proposed to utilize burner heads having a plurality of jetsfor playing flames over the surface to be hardened while rotating theflame with respect to the surface to be coated to uniformly distributethe heat to the entire surface. This process has been carried out withsome degree of success but has not proved entirely satisfactory in everyinstance, apparently because the application of heat to the surface tobe hardened has not been entirely uniform.

An object of this invention is to provide a process for surfacehardening solid metallic bodies wherein substantially all of the area tobe hard- .ened is subjected to continuous heating while the heater andwork piece are moved with respect to each other in a rotational sensewith the work piece serving as the center of rotation and in areciprocal sense along a straightline. I

Still a further object is to'provide a process for surface hardeningsolid metallic bodiessuch --as roller cutter bits wherein a granularhard substance is bonded to the surface to be hardened by playing flamecontinuously oversubstantially the entire surface to be hardened whilemoving the flame with respect'to each other as if the body were rotatedabout an axis passing through the body and reciprocated along a straightline. Yet another object is to provide a process for surface hardeningroller cutter bits wherein a flame is played over substantially theentire area of the 2 surface to be hardened while the flame and the bodyare moved with respect to each other as if the body were rotated aboutits axis and reciprocated along such axis.

Other and further objects to this invention will appear from thedescription.

In the accompanying drawings, which form a part of the instantspecification and are to be read in conjunction therewith and whereinlike reference numerals are used to designate like parts in the variousviews:

Fig. 1 is a schematic fra mentary side elevational view of apparatusembodying this invention with parts shown in section for added clarity:

Fig. 2 is a bottom plan view with parts in section of the apparatusshown in Fig. l. The process of applying hard surfacing material inaccordance with this invention includes the steps of securing the hardsurfacing material to the metal surface to which it is to be applied. Abinder of glue-like substance is employed to retain the surfacingmaterial upon the surface to be hardened and the oil, water or otherliquid vehicle is driven from the surface by suitable preliminaryheating. The coated surface is then heated, preferably with a gas flame,while the surface and the flame are kept moving with respect to eachother as if the body to be surface hardened were rotated about an axisthrough the body and reciprocated along a straight line passingtherethrough. During this heat ng operation. heat rays emanating fromthe surface under treatment are intercepted by a light or heat raysensitive element and the flame is controlled in accordance with theintensity of such intercepted heat rays so as to turn off the flame,when the intensity of the heat rays reaches a value which indicates thatthe surface to be heated has reached the desired temperature at whichthe hard surfacing material becomes bonded to 'th surface of the bodytreated.

Any suitable flame may be employed so long as it is given aconfiguration, such that it will heat the metal surface to which thehard surfacing material is to be applied, and the body-of metal adjacentsuch surface substantially evenly and uniformly. It is desirable thatthe surface to which the hard surfacing material is to be applied beheated to a temperature somewhat higher thanthe remainder of the body onwhich it is carried, but no great differential is required.

It has been found that the uniformness of application of heat to thesurface to be treated is unexpectedly increased when the surface to betreated is not only rotated with respect to the flame but is alsoreciprocated somewhat along a straight line, preferably the axis ofrotation. At any rate, it has been found that the end result of thehardening treatment is improved by this reciprocal movement and it isbelieved that this is due to greater uniformity in heating so thatsubstantially the entire area to be hardened will reach the desiredtemperature simultaneously without overheating any portion of it.

Where the member to be treated is a roller cutter of an earth drill bitwhich has an axis about which the parts to be surfaced are distributedmore or less regularly, it is desirable that the means for moving thesurface with respect to the flame be in the form of a spindle which maybe used to rotate the member and which may be axially reciprocated. I

Referring more particularly to the drawings, an apparatus capable ofcarrying out the process described is illustrated diagrammatically, andin this instance the body to which the hard surfacing material is to beapplied is in the form of aro'ller cutter I for an earth drill bit. Thiscutter has radially extending teeth 2 on its outer periphery and in theusual course of procedure in manufacturing these cutters, it is desiredthat one flank 3 of each such tooth be provided with a hard surface asby the application of tungsten carbide thereto and the bonding of *thetungsten carbide to the metal of the cutter.

The cutter is mounted upon a spindle or work piece holder 4 for rotationthereby and is'secured upon this spindle by means of a cap screw 5 andwasherlfi The speed of rotation is not critical but it has been foundthat a speed of between 25 and 300 R. P.'M. is suitable for the purposeof surfacing the teeth of the cutter of 6 to 8 inches in diameter.

Shaft 4 is journaled in a support 50'and preferably has a ball bearingmounting therein. The

rotated and moved axially at the same time.

The mechanism for imparting axial movement to the shaft includes bar 54pivoted to a support at 55 and :having at one end a roller whichoperates in groove 4b at the upper end of shaft 4. The-other end of bar'54 is connected to crank 56 by crank arm or link '51; The crank issecured to the shaft or rotatable member 58, by a suitable bolt. Member.58 may be rotated by-a suitable prime mover not shown in the drawings.With this arrangement it will be readily understood tha't'rotation of'member 58 will effect axial reciprocation of the work holder or shaft'4 to reciprocally shift the work piece 'I along a straight line, which,in this instance, is the axis for rotation of the'work-p'i'ece.

On each side of the cutter, as mounted upon the spindle 4, there isshown in the illustration suitable supports 1 and 8, similar to a lathebed,

and adapted to receive supports 9 and Ill mounted forsliding movementtoward and away from the spindle 4. The supports '9 and I9 are hollow,and connected with the hollow chamber thus formed in the support'9 areconduits [I and 12 for conveying to -such chamber a combustible fuelsuch as acetylene gas or the like and, if necessary, oxygen forsupporting combustion. Similarly conduits l3 and I4 are connected to thehollow interior of support 10 for supplying a combustible mixturethereto.

Support 9 carries a large burner head [5 and on lateral arms extendingfrom the burner head are carried relatively small auxiliary burner headsl6 and I1. Burner head I5 is positioned to direct a flame radiallyinwardly toward cutter teeth 2. The auxiliary burner heads arepositioned to direct a flame against opposite sides of the body of thecutter adjacent the roots of teeth 2. The auxiliary burner heads aresupported from a large burner head and form part thereof by means ofhollow arms l8 and I9, respectively.

.Arm It] carries a large burner head 20 directly opposed to the burnerhead and positioned to direct a flame radially inwardly toward the teeth2. Auxiliary burner heads 2! and 22 are carried by head and arepositioned on opposite sides of the cutter body adjacent the roots ofteeth 2.

These auxiliary burner heads are supported by hollow arms .23 and 24,the mounting being similar to that of the mounting of the auxiliaryheads 1-6 and IT.

' In order to prevent the back dash of flame into the burner heads,where gas such as acetylene, is employed, there is built into eachburner head aflame arrester structure which is preferably .cooledbywater .or the like. This coolant is applied to large burner head l5through conduits 25 to heater 20 through conduits 26 and auxiliaryburner heads IE, IT, 2| .and 22 .by conzduits .21, .28, .29 and 38,respectively.

Burner head I 5 is provided with burner tips '31, preferably adjustable,and arranged somewhat in the form of an arc to increase the uniformityof the application of heat to the teeth of the cutter. Large burner head20 is provided with tips .32, having a like arrangement. Auxiliaryburner heads [6, l1, 2| and 22 are provided respectively with burnertips 33, 34, .35 and 36. These latter tips are adjusted to such aposition that they will apply heat to those portions of the bodyadjacent-to the teeth at a rate which willheat such portions of the bodyof the. cutter at substantially the same rate that the teeth are heated.The opposed tips 33 and 34, 35 and 36 are spaced sufficiently far apartto permit the slight reciprocal movement of the work piece along itsaxis.

It will be seen that with this arrangement of burner tips that flanks 3of cutter teeth 2, as well as adjacent cutter surfaces, will besubstantially uniformly heated, the rotational and reciprocal movementbetween the flame and cutter adding to. the uniformity of heatdistribution over the surfaces to be treated.

Thesupply of gas and oxygen through conduits I l [2, I3 and i4 may bemanually controlled by suitable valves such as 31 and 38 andadditionally are controlled in accordance with this invention by meansof an automatic valve 39 which may be of any suitable well-knowntypesuch as the slide valve-illustrated having a double ported slide 40therein. It-will beseen that this slide 40 is constantly urged towardits right hand position by spring 4| and when in its right handposition, it will shut off the supply of oxygen and gas to all burners.This valve is intended to be moved to its left hand or open position, inwhich it is illustrated, by a suitable electromagnet 42 to which poweris supplied from a suitable source such as the battery 43. The supply ofthis power to member 42 'iscontrolled by a relay having a switch arm Mand an electromagnet'45, or by any other 5.. conventional device forclosing and opening the battery circuit in response to changes involtage supplied thereto. With the switch arm in illustrated position,electromagnet 42 will beenergized and the valve 39 opened, but whensufflcient current flows through the electromagnet 45, relay arm 44 willbe moved to the right and the circuit to the electromagnet 42 openedpermitting the spring 4| to close valve 39 and shut off the flames.

The current for electromagnet 45 is supplied by thermopile 46, within asuitable housing 41, and properly positioned, with respect to lens 48 sothat heat rays emanating from the teeth of cutter I will be focused uponthermopile 46. This thermopile may be incorporated in a closed circuit,including magnet 45 and recording indicator or ammeter 49. Ammeter 49may be calibrated in terms of the temperature of that part of the cuttersurface from which the heat rays intercepted by the thermopile emanate.

A specific example of this invention has to do with the coating over ofthe flanks 3 of the teeth of roller cutter l for earth drilling bitswith granular tungsten carbide. In this example the surfaces desired tobe coated are first covered or painted with a pasty water glass solutionand the tungsten carbide in granular form with grains of the size to beapplied to the surfaces of the teeth, is sprinkled upon the sodiumsilicate coating. The sodium silicate with the granular materialembedded therein is then thoroughly dried, and while under somecircumstances it may be sufficiently dried in air, preferably where thelater heat treatment is to be rapid the sodium silicate is subjected tosubstantial heat in order to drive off as much of the absorbed moistureand water crystallization as possible.

In order to prevent flaking of the binder from the covered surfacesduring the drying of the binder, the heating should be from the bodyoutwardly. By this means the moisture on the inner portion of the binderis first driven off before the outer coating becomes substantiallysolidified facilitating escape of the volatilized vehicle. This may beaccomplished by use of infrared rays directed upon the body or cutter.The proper drying may also be accomplished in an oven employing aninduction heater to heat the body of the cutter.

The dried and covered cutter is then placed upon spindle 4 and securedin place by cap screw 5 and washer 6. The various burners are startedand spindle 4 is rotated and reciprocated axially whereby the heat fromthe flames is uniformly distributed to the surface of the cutter to beheated.

The heat rays from the cutter teeth, which will heat a little faster andhence are always at a slightly higher temperature than the body of thecutter, will pass from the teeth just as they emerge from the flame ofone of the large burners and will be focused by lens 48 upon thermopile46. The thermopile and relay coil 45 are proportioned so the currentfrom thermopile 46 will not actuate the relay until the intensity of theheat rays intercepted by the thermopile corresponds to the intensity ofsuch rays when the surfaces of teeth 2 will just begin to alloy with thetungsten carbide and fuse along that part thereof which is in contactwith the tungsten car bide. When this temperature of the teeth surfaceis reached relay 45 will automatically .open to de-energizeelectromagnet 42, whereby spring 4| will move valve member 40 to itsclosed position, cuttin'g'ofi the source cf'combustible 'mix-' Thecutter is then permitted drous sodium silicate serves asra binder toretain the tungsten carbide particles upon the cutter teeth while themetal of the cutter teeth reaches its requisite temperature for thebonding of the tungsten carbide materials thereto. I

It will'be appreciated that by this invention a process of applying hardsurfacing material to a metal surface has been provided wherein it ispossible to accurately control the application of heat to the metalsurface and wherein the surfaces treated will be uniformly heated due tothe arrangement of burner jets and the rotational and axial reciprocalmovement of the work piece. By maintaining the flames employed in theheating operation as reduction flames the surface of the cutter will notbe excessively burned or oxidized.

It is to be understood that while this process is especially adapted tothe hard surfacing of the teeth of rotary cutter for earth drillingbits, the process and apparatus of this invention are not limited tosuch use but may be employed in many other types of work where it isdesired to surface harden material wherein the application of heat isrelied upon and must be uniformly distributed over the surface treated.

Having described the invention, what is claimed 1s:

1. The process of applying hard surfacing material to the teeth of arotary metal cutter for an earth drilling bit, which comprises coveringthe teeth with a pasty sodium silicate solution, embedding hardsurfacing material in a granular form upon the covered surface, heatingthe sodium silicate by heating th metal of the cutter and utilizing theheat radiating from the metal of the cutter to drive substantially allof the liquid vehicle from the sodium silicate, rotating the cutter andaxially reciprocating the cutter while playing a flame upon said teeth,impinging the heat waves emanating from said cutter teeth onto anelectric heat responsive element thereby indicating an electric voltageproportional and representative of the intensity of said heat waves, andstopping the heating of the cutter when said electric voltage attains apredetermined value indicating the temperature of the surface of thecutter teeth, at which the metal of the surface forms a bond with thehard surfacing material.

2. The process of applying granular tungsten carbide to a surface of ametallic body, which comprises covering the surface to be hardened witha binder comprising a pasty sodium silicate solution, embedding the hardsurfacing material in granular form in the binder cover-ing, applyinginfrared heat rays to said body to drive substantially all the moisturefrom the binder solution, rotating the body and axially reciprocatingthe body while playing a source of heat upon said body to heat thesurface thereof, impinging the heat waves emanating from said bodysurface onto an electric heat responsive element thereby indicating anelectric voltage proportional and representative of the intensity ofsaid heat waves and stopping the heating of the body surface when theintensity of said heat waves reaches a. 1.8.1116; indicating; that; thetemperature: of the Number the-point ail-which: the,:meta1 of the1,902,092. surf-ace; W111 become;- bonded; with; the; tungsten.2043,7211 carbide. $215,576; CHARLES. H. 5 2258394 2,261,228 REEERENCESGIT-ED 2377 541 The following references are of record: in the 5, fileof this patent: l0

UNITED STATES. PATENTS 2326103 Number Name Date 2,416,1 I

1,149,917 Jamison et, a1. Aug. 10., 1915 1,280,889 Spang Oct. 8,, 19-181,575,635 Meker Mar. 9, 1926 15' Number 1,735,000 Dely- Nov. 12,,1929540,270 1,824,121: Charlton Sept. 22,1931 596,626

Name; Date,- N0rwood\ Mar. 21-, 1933 wagenhals June 9,1936 Bucknamt e1:a1; Sept. 24, 1940; Janco: 00's., 14,. 1941 Cockrum Nov; 4,,51941MerIub-Sobel' et a1. Mar. 24', 1942 wissler" Sept. 15', 1942 Wagner Nov.10, 1942' Quinn June 15; 1943 Snyder Aug. 10, 1943 Beck Feb. 18, 1947'FOREIGN PATENTS" Country Date GreatBritaJin- Oct. 10-, 1941 Great?Britain Jan. 7, 1-948

1. THE PROCESS OF APPLYING HARD SURFACING MATERIAL TO THE TEETH OF AROTARY METAL CUTTER FOR AN EARTH DRILLING BIT, WHICH COMPRISES COVERINGTHE TEETH WITH A PASTY SODIUM SILICATE SOLUTION, EMBEDDING HARDSURFACING MATERIAL IN A GRANULAR FORM UPON THE COVERED SURFACE, HEATINGTHE SODIUM SILICATE BY HEATING THE METAL OF THE CUTTER AND UTILIZING THEHEAT RADIATING FROM THE METAL OF THE CUTTER TO DRIVE SUBSTANTIALLY ALLOF THE LIQUID VEHICLE FROM THE SODIUM SILICATE, ROTATING THE CUTTER ANDAXIALLY RECIPROCATING THE CUTTER WHILE PLAYING A FLAME UPON SAID TEETH,IMPINGING THE HEAT WAVES EMANATING FROM SAID CUTTER TEETH ONTO ANELECTRIC HEAT RESPONSIVE ELEMENT THEREBY INDICATING AN ELECTRIC VOLTAGEPROPORTIONAL AND REPRESENTATIVE OF THE INTENSITY OF SAID HEAT WAVES, ANDSTOPPING THE HEATING OF THE CUTTER WHEN SAID ELECTRIC VOLTAGE ATTAINS APREDETERMINED VALUE INDICATING THE TEMPERATURE OF THE SURFACE OF THECUTTER TEETH, AT WHICH THE METAL OF THE SURFACE FORMS A BOND WITH THEHARD SURFACING MATERIAL.